This section is intended to introduce the reader to various aspects of the art that may be related to various aspects of the present invention. The following discussion is intended to provide information to facilitate a better understanding of the present invention. Accordingly, it should be understood that statements in the following discussion are to be read in this light, and not as admissions of prior art.
Heart failure (HF) is one of the leading causes of admission to the hospital.1 Studies have shown that patients with dilated hearts have a reduction in the frequency of hospital admission and prolongation of life with the implantation of bi-ventricular pacemakers and automatic implantable cardiac defibrillators (AICDs).2-5 These benefits extend to the millions of patients with both ischemic and idiopathic cardiomyopathy. Recently, “piggybacking” technology onto AICDs and bi-ventricular pacemakers for sensing the progression of impending heart failure to reduce the number and length of stay of hospital admissions for CHF has been proposed.6-14
Currently, the only way to tell if cardiac output is being maximized by a timing algorithm (or using bi-ventricular pacing) is to use imaging methods such as echocardiography which require trips to the hospital, and trained physicians to both perform the measurements and interpret results. The body of literature shows that pacemaker timing optimization improves outcomes in patients, and that there would be immediate benefit for a new device, which performed this calibration automatically.    [1] Bordachar P, Garrigue S, Reuter S, Hocini M, Kobeissi A, Gaggini G, Jais P, Haissaguerre M, Clementy J, Hemodynamic assessment of right, left, and biventricular pacing by peak endocardial acceleration and echocardiography in patients with end-stage heart failure. Pacing Clin Electrophysiol 2000; 23:1726-1730.    [2] Bordachar P, Labrousse L, Ploux S, Thambo J B, Lafitte S, Reant P, Jais P, Haissaguerre M, Clementy J, Dos Santos P: Validation of a new noninvasive device for the monitoring of peak endocardial acceleration in pigs: implications for optimization of pacing site and configuration. J Cardiovasc Electrophysiol 2008; 19:725-729.    [3] Gorcsan J, 3rd, Abraham T, Agler D A, Bax J J, Derumeaux G, Grimm R A, Martin R, Steinberg J S, Sutton M S, Yu C M: Echocardiography for cardiac resynchronization therapy: recommendations for performance and reporting—a report from the American Society of Echocardiography Dyssynchrony Writing Group endorsed by the Heart Rhythm Society. J Am Soc Echocardiogr 2008; 21:191-213.    [4] Hasan A: How Should Echocardiography Be Used in CRT Optimization? J Am Soc Echocardiogr 2010; 23:867-871.    [5] Klimczak A, Chudzik M, Zielinska M, Budzikowski A S, Lewek J, J K W: Optimization of atrio-ventricular delay in patients with dual-chamber pacemaker. Int J Cardiol 2010; 141:222-226.    [6] Taha N, Zhang J, Ranjan R, Daneshvar S, Castillo E, Guillen E, Montoya M C, Velasquez G, Naqvi T Z: Biventricular pacemaker optimization guided by comprehensive echocardiography-preliminary observations regarding the effects on systolic and diastolic ventricular function and third heart sound. J Am Soc Echocardiogr 2010; 23:857-866.    [7] Kedia N, Ng K, Apperson-Hansen C, Wang C, Tchou P, Wilkoff B L, Grimm R A: Usefulness of atrioventricular delay optimization using Doppler assessment of mitral inflow in patients undergoing cardiac resynchronization therapy. Am J Cardiol 2006; 98:780-785.
The problem with constant rate pacemakers (and indeed adaptive pacing) is that the problem is not closed-loop. That is to say, there is no method for quantifying success continuously in pacing without the need for an expensive doctor visit. This invention will help to close the loop and provide the best possible pacing algorithm in both bi-v, and normal pacemakers, also allowing the device to self-calibrate for the first time.
The idea of multisite pacing has been shown to improve outcomes in patients receiving a multi-site pacing device. Additionally, optimization of multi-site pacing by maximizing stroke volume and ejection fraction, and minimizing end-systolic volume, has been shown to improve quality of life in patients using comprehensive echocardiography. However, proponents of this technology recognize that it is still too time, resource, and labor intensive. The new approach described in this invention will allow a measurement of real time stroke volume, end-systolic volume and ejection fraction coupled to existing bi-ventricular pacing leads already implanted within a patient. This new information will allow the use of a self-calibrating algorithm, which is simple, accurate, and shortens the doctor-patient interaction time. A self-calibrating pacemaker timing will outperform a one-time programmed pacemaker by requiring less trips to the doctor's office for calibration, saving the patient time and money, and also has the potential to perform better than a normal pacemaker, because it is tailored more closely to the patients needs.
Regarding alternative technologies which use electric fields, there are two which have been “piggybacked” onto bi-ventricular pacemakers and AICDs that have been tested in clinical trials. First, Chronicle® measures right heart pressures in an attempt to monitor increases that are indicative of heart failure.6, 7, 9 Second, Optivol® and CorVue™ use lung conductance measurements as an indication of pulmonary edema.8, 11, 12, 14 However, neither measures LV volume and thus they cannot be used to tune these pacing devices and maximize LV stroke volume and ejection fraction. More recently Stahl et al.13, 15 have proposed generating an electric field in the RV, and detecting the fringe field from the LV bi-ventricular pacer lead. However, this measurement does not separate the lumped blood and myocardial components. Thus, there are currently no proposed technologies that can perform LV blood volume measurements.